Incorporating Residential Self-Selection Effects in Activity Time-Use Behavior: Formulation and Application of Joint Mixed Multinomial Logit-Multiple Discrete-Continuous Extreme Value Model.

This study presents a joint model system of residential location and activity time-use choices that considers a comprehensive set of activity-travel environment (ATE) variables, as well as sociodemographic variables, as determinants of individual weekday activity time-use choices. The model system takes the form of a joint mixed Multinomial Logit Multiple Discrete-Continuous Extreme Value (MNL-MDCEV) structure that (a) accommodates differential sensitivity to the ATE attributes due to both observed and unobserved individual and household attributes, and (b) controls for the self selection of individuals into neighborhoods based on observed and unobserved activity time-use preferences. The joint model system is estimated on a sample of 2793 households and individuals residing in Alameda County in the San Francisco Bay Area. The model results indicate the significant presence of residential sorting effects based on time-use preferences. For instance, individuals with bicycles locate themselves into neighborhoods with goodbicycling facilities. These same individuals also have a preference for physically active pure recreation pursuits. Ignoring this effect of bicycleownership would lead to an inflated estimate of the effect of bicycling facility density on time invested in physically active recreation. Similarly, there are unobserved individual factors (such as fitness consciousness)that make individuals locate in areas with good bicycling facilities and also lead to a high preference for physically active recreation. That is, people who are predisposed to physically active lifestyles tend to self-select themselves into zones with very good bicycling facility density for their residence. These results show the danger of ignoring residential sorting effects when estimating the effects of the activity-travel environmenton activity-travel choices. Nevertheless, the findings from our study indicate that modifying the activity-travel environment can lead to small changes in individual activity time-use patterns, even after controlling for residential sorting effects.